I think the biggest question here is what saves more dirty energy. Obviously, these units will compete with solar for roof space. The sun beats down in the summer, where these panels would be most useful, but also where solar would hit peak power generation. As long as solar can supply at least 20% of the power required to cool the building, it seems like it will be a better option, as solar is also useful for other things like charging electric cars during the winter, when A/C is not required.